Telecommunications has evolved from transmitting only voice to a multimedia vehicle for communication. Modern users of telecommunications services are supported by subscriber lines which not only transmit voice but also send data transmissions generated by facsimiles and Internet access. A common implementation of a modem subscriber line interconnects a twisted cable pair from a subscriber's customer premises equipment to a subscriber line card associated with a digital switching system. The line card provides functions of battery, overvoltage protection, ringing, supervision, hybrid and testing (commonly referred to as the BORSHT functions) and converts analog voice band frequencies into a stream of pulse code modulation octets carried at 64 kilobits per second across the digital switching system and the rest of the public-switched telecommunications network (PSTN).
Current line card implementations operate in a mode for optimizing voice transmission. The transmission of data signals requires use of modulator/demodulator devices (modems) for transforming digital data signals into analog signals which are carried within the standard voice band frequency limitations of the telecommunications network. Current voice band frequency limitations of the PSTN hold the per subscriber line modem data transmission rate to approximately 56 kilobits per second. Unfortunately, the 56 kilobits per second transmission rate is unacceptably slow for many telecommunications service subscribers who routinely send data via the PSTN. To obtain higher transmission rates, it is common for these subscribers to bind two or more analog subscriber lines together through special modems working in the role of inverse multiplexers. Special modems, or any increase in the number of lines used per subscriber, are problematic because of the increase in average holding time of all telephone calls served by the switch. Further, increased subscriber line usage invalidates current standards for concentration of subscriber lines per switch and the provisioning of intraswitch time slot facilities.
The real-life impact of an increase in concentration of subscriber lines per switch is the more frequent denial of dial tone or the receipt of busy signals by subscribers who are accustomed to consistent and reliable access to the PSTN. The current state of subscriber line concentration is especially troubling since switch resources are unnecessarily occupied. This is because a significant amount of data transmissions between a subscriber line and the PSTN carry idle data (that is, non-useful packets of information) which is a well known and common phenomenon of data connections. Therefore there is a need in the art for decreasing the occurrence of blocked access to the telecommunications network while efficiently accommodating prolonged data transmissions.